1. Field of the Invention
The present invention relates to an electrophotographically information recording method of recording the information, which is supplied in the form of electric signals from an information device such as an electronic computer, as a visible image on recording paper by forming the image as an electrostatic latent image on a photosensitive element and then by electrophotographically treating the electrostatic latent image. More specifically, the present invention relates to an information recording method which can facilitate the discriminations between the sheets of the recording paper containing different pieces of information and which can minimize the reduction in the treating capacity due to an information source having a low information transfer speed.
2. Description of the Prior Art
Recently, the electrophotographic recorder as shown, for example, in U.S. Pat. No. 4,134,668 has been being used in the terminal device of a computer, an output device of the information to be transmitted through a communication circuit or the output reader of a facsimile. In one mode of the electrophotographic recorder, the information, which is supplied in the form of electric signals from the outside, is converted into an optical image by means of a scanning reproducer such as an optical fiber tube, a thin-window recording tube, needle electrode or a laser beam scanner so that it is recorded as an electrostatic latent image on a photosensitive element which is uniformly charged. The electrostatic latent image is developed with a developing agent into a visible image, which is either fixed as a recorded image as it is or transferred to the recording paper and then fixed to produce a final picture image. A series of the treating steps to treat the electrostatic latent image thereby to produce the final picture image are called the electrophotographic treatment and are adopted in the usual electrophotographic copier. The electrophotographic treatment includes the steps of uniformly charging a photosensitive element by turning a photosensitive drum at a constant speed, forming an electrostatic latent image by projecting an optical image upon the photosensitive element charged, developing the electrostatic latent image with a developing agent, transferring the developed image to recording paper, thermally fixing the transferred image, while removing the charges left on the surface of the photosensitive element after the transfer, and cleaning the toner left on the surface of the photosensitive element. The time period required for the original exposing step for forming the electrostatic latent image; and for the treating cycle of one electrophotograph is constant, and a sheet of copied image is recorded usually for one electrophotographically treating cycle. Thus, because the electrophotographic treatment is adopted, a time period, which is predetermined by the series of the treating steps, is required for the electrophotographic information recorder to accomplish the recording treatment. In the electrophotographic information recorder according to the prior art, therefore, the feed of the recording paper is performed each predetermined time so that the number of the sheets of the recording paper to be treated for the predetermined time is accordingly determined. For example, the copying time of one sheet is 6 seconds for intermittent copying and 2 seconds for continuous copying.
On the other hand, the information to be recorded by the electrophotographic information recorder is supplied in the form of electric signals from the outside and is generally various from remarkably quick to remarkably slow because of the variety in the performance of the information processing device to be connected therewith. For example, there is an information source such as a magnetic tape, by which much information transfer is effected within a short time period, or an information source such as a punched tape, by which it takes much time to transfer the information. Generally, 110 characters per second can be transferred in case of punched tape and 9,600 characters per second can be transferred in case of TELETYPE (Trade Name), whereas 3,000 characters can be stored on one sheet. For the interval between one electrophotographic treating cycle and the subsequent electrophotographic treating cycle, the information to be recorded during the subsequent electrophotographic treating cycle is introduced from an external information source and is transformed into a video signal. Because of the variety in the transfer speed and quantity of the information, however, the constant time interval, which is predetermined by the electrophotographic treatment, may be either short or sufficient for the introduction and transforming of the information.
If the information processing device has a sufficient capacity, external information to be subsequently recorded can be received and transformed while recording the preceding information on the photosensitive element. However, it is impossible to do if the information processing device has not such a large capacity that the quantity of information corresponding to more than single sheet or page of the recording paper can be stored. Such information processing device having a large capacity causes the construction to be complicates and the cost to be increased.
According to the usual electrophotographic information recorder, on the other hand, since the time period required for the electrophotographic treatment is constant irrespective of the levels in the quantity and transfer speed of the information to be recorded, the number of sheets of the recording paper to be treated for the present time period is restricted. In the electrophotographic information recorder, therefore, the preset information introduction time relating to the electrophotographic treatment is predetermined. In the recorder thus far described, in case the transfer speed of the information to be recorded is so low that the information introduction is not completed within the predetermined information introduction time, the subsequent electrophotographic treating operations are interrupted, but the information introduction itself is continued. After that, the electrophotographic treating operations are started again from the instant, when the information introduction is completed, thus practising the recording operations. However, as the voltage circuit for applying a high voltage on electrodes such as a charging electrode, a charge removing electrode and a separating electrode has a high time constant, it takes much time to reach the voltage at a predetermined level. A predetermined sufficient elapse time has to be taken especially for the charging operation of the photosensitive element which will determine the quality of the picture image. Accordingly, a considerable time of, for example, at least several seconds is wasted before the electrophotographic treating operations are started again after the information introduction is completed. This is not desired in view of the effective use of the recording time. This effective use of the recording time is an important problem especially when it is considered that the electrophotographic information recorder is used for the terminal device of the computer or the output device of the information to be transmitted through the communication circuit, which device is used to process the information to be transferred at a high speed.
Moreover, the case, in which the external information is recorded by the electrophotographic recorder of this kind, is divided into the case, in which the same information is recorded in a single sheet, and into the case in which the information is recorded in plural sheets. In case different pieces of information are to be recorded in multiple sheets, it is convenient that those sheets of the recording paper are recognized for the different pieces of information. For this reason, it is sufficient that the discriminating paper such as color paper or tape is inserted between the different sheets of the recording paper. For this purpose, there have conventionally been proposed a variety of methods for inserting the discriminating paper. In one example proposed, a color tape is prepared for the discriminating paper independently of the recording paper and when it is detected that the information to be recorded is different, the feeding and cutting mechanisms of the color tape are controlled in accordance with the movements of the recording paper thereby to insert the cut sheet of the color tape between the sheets of the recording paper to be discharged. Another mechanism is made so similar to the above as to include a discriminating paper feeder and a controller which is operative to control the feeder in relation to the operation of the recording paper. In addition to these recording paper feeder and controller which are intrinsic, therefore, a discriminating paper feeder and its control system are required with the resultant disadvantage that the recorder has its construction complicated to raise the production cost.